1. Field of the Invention
The present invention relates to a method for manufacturing a field effect transistor.
2. Related Background Art
In recent years, flat image display devices (Flat Panel Display: FPD) have been developed for practical use as a result of the progress made in technologies such as liquid crystals and electroluminescence (EL). These FPDs are driven by the active matrix circuitry of field effect thin-film transistors (Thin Film Transistor: TFT) which use an amorphous silicon thin-film or a polycrystalline thin-film on a glass substrate in the active layer.
Meanwhile, testing is being carried out into the use of resin substrates which are light-weight and flexible in place of a glass substrate in order to make such FPDs even thinner, lighter and have better their shatter resistance.
However, the manufacture of such an above-described transistor which uses a silicon thin-film requires a relatively high temperature thermal process, whereby direct formation onto a resin substrate, which usually has a low thermal resistance, is difficult.
Therefore, development is being actively conducted into TFTs which are capable of deposition at low temperatures and which use, for example, ZnO as a material for the oxide semiconductor thin-film (Japanese Patent Application Laid-Open No. 2003-298062).
From the knowledge of the present inventors that ZnO cannot generally form a stable amorphous phase, existing mainly in a polycrystalline phase, carriers would therefore be scattered at the interface between polycrystalline particles. As a result of this fact, it was learned that electron mobility cannot be increased.
That is, a method has been sought for producing an amorphous oxide which can be preferably used in the active layer of a field effect transistor.